Commercial and other buildings are regularly insulated and waterproofed by applying multicomponent coatings by spraying. As an example, roofs of commercial buildings are waterproofed by applying a polyurethane foam. The polyurethane foam is produced by pumping and spraying desired proportions of polymeric isocyanate and resin components.
In these systems, two or more components having different viscosities must be accurately metered throughout the spraying process. In spraying polyurethane foam, a one to one ratio is normally required. In other multicomponent organic resin sprays, such as for fire retardants and other insulations, a different ratio may be required. Further, these materials, because they must be mixed immediately prior to application to avoid premature set up, must be very accurately metered and sprayed at precise pressures and temperatures to achieve appropriate atomization of both components and their mixture. If the components are not properly proportioned, the coating may not properly set up and may not attain the intended properties.
Heretofore, substantial equipment has been required to accomplish the spraying of these multicomponent coatings and portable units have not existed. In most prior art systems, piston pumps are used for pumping each of the components. These systems are designed for large spray jobs, such as where an entire building roof is to be insulated. While the same systems are also used for small repair jobs, the bulk and size of the equipment makes this undertaking extremely costly.
In the prior systems which use piston pumps, it has been difficult to maintain a proper ratio of one component to the other at all pumping rates and conditions. Further, maintaining equal pressure of both components is difficult. Moreover, these problems are exasperated where small jobs are attempted.
For metering and applying dual component materials, only one system is known which uses gear pumps. This system, disclosed in a patent to the inventor of the present invention, U.S. Pat. No. 4,376,512, uses identical dual gear pumps driven by hydraulic motors connected in series. While this system operates satisfactorily for its intended purpose, it does not achieve the object of the present invention to provide a system which may be designed to easily and accurately proportion two or more different components being pumped.